Iodine deficiency and excess in children: worldwide status in 2013.

Assessing iodine nutrition at the population level is usually done by measuring the urinary iodine concentration (UIC) and, in some countries, by estimating household coverage of adequately iodized salt (HHIS). Using these indicators, the objective of this review is to assess global and national iodine status in 2013. The most recent data on HHIS were obtained from the United Nations Children's Fund. The most recent data on UICs were obtained from the International Council for the Control of Iodine Deficiency Disorders Global Network and the World Health Organization (WHO). Median UIC was used to classify national iodine status based on the current WHO classification system, with the following modification: the "adequate (100 to 199 μg/L)" and "more than adequate (200 to 299 μg/L)" categories of median UIC in school-aged children were combined into a single category of "adequate" iodine intake (100 to 299 μg/L). Over the past decade, the number of countries that are iodine deficient has fallen from 54 to 30. The number iodine-sufficient countries has increased from 67 to 112, while the number with excessive iodine intake has increased from 5 to 10. In most countries with excess intake, this is due to overiodization of salt and/or poor monitoring of salt iodization. Out of 128 countries with HHIS data, at least 90% of households in 37 countries consume adequately iodized salt, but in 39 countries, coverage rates are below 50%. Overall, about 70% of households worldwide have access to iodized salt. There has been substantial recent progress in the global effort to control iodine deficiency. However, iodized salt programs need to be carefully monitored to ensure adequate iodine intake while avoiding iodine excess.